The invention relates to diversity receivers, and in particular to selecting a receiver among a plurality of receivers in a diversity receiver system based upon automatic gain correction.
Diversity receiving systems with several receivers are used, for example, in vehicles. The receivers can be for example audio and video receivers.
Reception and reproduction of video pictures in stationary receiving stations poses no difficulties, because the reception conditions remain largely constant. On the other hand, the reception conditions for a mobile receiving station can vary considerably, depending on the nature of the terrain. For instance, if the mobile receiving station is situated in mountainous terrain, echoes can cause considerable interference with reception. In the radio shadow of mountains or hills, the radio connection can even break down completely, so that, in place of a video picture, only noise is visible on the screen.
In the meantime, motor vehicles such as, for example, passenger cars, long-distance buses, and railroad cars, are being equipped with television receivers and screens, so that messages can be displayed, for example traffic reports sent by video text, or, the travelers can be entertained with television programs. The receiving conditions in a moving receiving station vary considerably in some circumstances, due to the terrain through which the receiving station is currently passing. Consequently, this will subject the travelers who are watching television to unpleasant and considerable eye strain, because the picture quality can vary to a great extent. For example, if the vehicle is passing through a radio shadow, the viewers will see only noise on the screen. Looking at a television program with such interference subjects the viewers to fatigue rather than entertainment.
It is known that the reception of radio signals in mobile receiving stations can be improved by multi-path reception, also referred to as “diversity.” By antenna diversity is understood a receiver which can be connected to one of several antennas, generally spatially separated from one another, while by frequency diversity is understood a system consisting of several receivers which receive the same signals or the same programs on different frequencies. The signals delivered by the antennas in the case of antenna diversity and by the receivers in the case of frequency diversity are tested for their quality so as to forward and process the best quality signal.